Networking Basics CCNA 1 Chapter 5

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Networking Basics CCNA 1Chapter 5

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Cabling LANs

Line Styles for Cables Used in Network Diagrams

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Cabling LANs

Ethernet LAN Physical Layer• Earliest Ethernet standards used coaxial cabling• Today’s standards called for twisted-pair (usually

UTP) or fiber-optic cabling• IEEE separated Ethernet into two standards

– IEEE 802.2 - Logical Link Control (LLC) sublayer defines part of the OSI data link layer

– IEEE 802.3 – Media Access Control (MAC) sublayer also defines part of the OSI data link layer

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Cabling LANs

Ethernet LAN Physical Layer (continued)

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Cabling LANs

Ethernet LAN Physical Layer Design Considerations

• Does maximum cable length allowed meet segment requirements

• Cost of cable• Cost of equipment on ends of cable• Which cables support which Ethernet speeds• Ease of installation• Susceptibility to interference

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Cabling LANs

Choosing Ethernet Types (Speeds) in the Campus

• Network engineers must consider speed of Ethernet types

• Most current PCs have 10/100 Mbps NICs – means a current design would use 100 Mbps Ethernet on the LAN

• Most new PCs come with 10/100/1000 Mbps NICs – must consider expense of upgrading LAN switches to 1000 Mbps (1 Gbps)

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Cabling LANs

Three Types of Ethernet Links• End-user level – Links between a hub/switch

and end users’ computers• Workgroup level – Links between the

hub/switch that attach to end users’ computers and other hubs/switches in the LAN core

• Backbone level – Links between the hubs/switches in the LAN core

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Cabling LANs

Campus LAN with Online

Curriculum’s LAN Level

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Cabling LANs

Ethernet Types and Speeds Used on Various Link Types per Online Curriculum

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Cabling LANs

Ethernet Types and Speeds Used on Various Link Types – Best Practices

• End-user level: 100 Mbps

• Workgroup level: 1 Gbps

• LAN Core (Backbone): 1 Gbps or 10 Gbps

• Remember, speeds will increase as the technology evolves

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Cabling LANs

Components of the Campus Design Model• Access switches and links – end-user devices

connect to access switches (LAN switches), with Ethernet links called access links

• Distribution switches and uplinks – a large number of access switches connect to a smaller number of distribution switches; the links between them are called uplinks

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Cabling LANs

Components of the Campus Design Model (continued)

• Building block – a single building’s design with access and distribution switches

• Core switches and links – in large campuses, each building block is connected to very fast core switches, using core links

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Cabling LANs

Ethernet Types, Media and Segment Lengths

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Cabling LANs

Ethernet Types, Media and Segment Lengths (continued)

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Cabling LANs

Ethernet Types, Media and Segment Lengths• Using the charts is important to the LAN planning

process• Most paths between devices are not straight line• After media are selected, cables with appropriate

connectors must be ordered or made• Some older NICs and networking devices use

attachment user interface (AUI) connectors

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Cabling LANs

Common LAN Cable Connectors

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Cabling LANs

Picking UTP Cable Pinouts• Straight-through – use TIA/EIA-T568-A or

TIA/EIA-T568-B on both ends• Crossover (10BASE-T and 100BASE-TX) - use

TIA/EIA-T568-A on one end and TIA/EIA-T568-B on the other end

• Crossover (1000BASE-TX) – use TIA/EIA-T568-A on one end and swap the orange/green (pairs 1 and 2) and blue/brown pairs (pairs 3 and 4) on the other end

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Cabling LANs

TIA/EIA-T568-A and TIA/EIA-T568B Pinouts

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Cabling LANs

10BASE-T and 100BASE-TX Crossover Cable

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Cabling LANs

1000BASE-T Crossover Cable

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Cabling LANs

Crossover Cables• Many products, including Cisco switches,

us Auto Medium-independent Crossover (Auto-mdix)

• Detects when a cable with wrong pinouts is connected

• Automatically makes internal changes to make connection work

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Cabling LANs

Choosing When to Use Straight-Through and Crossover Cables

• Devices that transmit at pins 1 and 2: PCs, routers, servers, wireless access points’ Ethernet ports

• Devices that transmit at pins 3 and 6: hubs, switches, bridges, repeaters

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Cabling LANs

• Use a straight-through cable to connect– Switch to router– Switch to PC or server– Hub to PC or server

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Cabling LANs

• Use a crossover cable to connect– Switch to switch– Switch to hub– Hub to hub– Router to router– PC to PC– Router to PC

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Cabling LANs

• Cisco prints an “X” on ports that transmit on pins 3 and 6 instead of pins 1 and 2

• This denotes they are internally crossed over

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Cabling LANs

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Cabling LANs

Connecting Ethernet Networking Devices• Must play close attention to distances between

devices• Must consider how extending the length of the

network by adding devices has an impact

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Cabling LANs

Connecting Ethernet Networking Devices

• Repeaters– Extend the distances over which an Ethernet

network can send data– Receives a degraded signal, cleans it up and

retimes it, and sends it out the other port– Cannot indefinitely extend a LAN

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Cabling LANs

• Repeaters– 5-4-3 rule

• At most 5 cables in the LAN• At most 4 repeaters• At most 3 cables can have PCs attached

– Allows for maximum distance of 500 meters

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Cabling LANs

Basic Function of a Repeater

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Cabling LANs

Connecting Ethernet Networking Devices• Hubs

– IEEE created 10BASE-T and hubs to overcome problems with older Ethernet standards

– Old standard called for a physical bus topology– New standard allows a physical star topology– Thinner cable makes installation easier– Maximum single cable length of 100 m, versus 185 m

and 500 m

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Cabling LANs

Connecting Ethernet Networking Devices• Hubs (continued)

– 10BASE-T allows the use of hubs and repeaters– Similar to repeaters, hubs receive a signal on one

port, regenerate it, and send it out all other ports– Hubs contain multiple RJ-45 jacks to provide a place

to connect multiple UTP cables, which creates the physical star topology

– Hubs are sometimes called “multiport repeaters” or “concentrators”

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Cabling LANs

10BASE-T with Hub Operation

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Cabling LANs

Comparing the Three Types of Ethernet Hubs

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Cabling LANs

Connecting Ethernet Networking Devices• Bridges

– Use logic to decide whether to forward frames– This logic is closely matched to OSI Layer 2, so

bridges are considered to be Layer 2 devices– Bridges use this process:

• Examine incoming frame, look at destination MAC address• If destination MAC is reachable via a different interface than

the one one which it was received, regenerate and forward out that interface (forward)

• If destination MAC is on the same interface it arrived on, discard the frame (filter)

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Cabling LANs

Bridge Making a Filtering Decision

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Cabling LANs

Bridge Making a Forwarding Decision

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Cabling LANs

• Ethernet switches– Provide all the benefits of repeaters, hubs and

bridges– Most LANs use switches instead of hubs or

bridges– LANs need repeaters only when very long

runs are needed

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Cabling LANs

Connecting Ethernet Networking Devices• Functions of an Ethernet Switch

– Like a hub, provides a large number of ports for making a physical star topology

– Like repeaters, hubs and bridges, regenerates a clean signal

– Like bridges, uses filtering/forwarding logic– Like bridges, separates a LAN into multiple collision

domains, increasing LAN bandwidth– Beyond the functions of hubs, repeaters, and bridges, offers

advanced features such as virtual LANS (VLANs) and much faster performance

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Cabling LANs

Switch Making a Forwarding

Decision

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Cabling LANs

Connecting Ethernet Networking Devices• Functions of an Ethernet Switch (continued)

– Uses a switching table much the same way a bridge uses a bridging table - Cisco switching table is sometimes referred to as Content Addressable Memory (CAM) table

– Allows devices to send data at the same time without collisions by using full-duplex logic

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Cabling LANs

Switch with Four 100 Mbps Ports – 400 Mbps

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Cabling LANs

Wireless Communications and Wireless Access Points

• “Wireless” does not mean just WLANs or Wi-Fi

• Includes most every type of electromagnetic (EM) energy– Radio waves– Microwaves– Infrared light

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Cabling LANs

• Infrared (IR) and radio frequencies (RF) are both popular for wireless communication today

• IR requires line-of-sight between sending and receiving devices (TV remote control and TV)

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Cabling LANs

• RF has been used for communications for more than a century: AM/FM radio, Airplane to control tower, Police and fire departments

• Does not require line-of-sight• Wireless devices designed for two-way communication

need a transmitter and a receiver• WLAN standards use a range of frequencies called a

spread spectrum

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Cabling LANs

WLAN Review• Wireless Access Points (APs)

– Have much in common with hubs and switches– Provide a centralized connection point (without wires)– Have limitations on distance– Like hubs, create a shared medium– PCs and laptops use wireless cards, so no networking

cables are needed– The AP connects to the rest of the network with a

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Cabling LANs

AP, Switch, and Hub Used for End-User Device Access

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Cabling LANs

Ethernet NICs• NICs – expansion PC cards that create a way for

the PC to connect to a network• Must operate and OSI Layers 1 and 2• Layer 1 – send and receive signals over an

attached cable• Layer 2 – they frame data inside a header and

trailer, with header including Layer 2 address called the Media Access Control (MAC) address

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Cabling LANs

Ethernet NICs• Network diagrams do not usually show the NIC

as it is assumed each PC has one• On laptops, the NIC might be built in or in a small

expansion slot called a PC card slot

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Cabling LANs

Ethernet NIC: Circuit Board Internal to the PC

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Cabling LANs

Ethernet NIC: External Portion with RJ-45 Connector

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Cabling LANs

Ethernet NICs• Most NICs use an RJ-45 connector• Older NICs can be replaced or an adapter can be

used (older routers, e.g., may need an AUI connector for their Ethernet ports

• The use of an AUI means the device does not need to have an internal transceiver

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Cabling LANs

Using the LAN: Models for PC Communication

• Computers on a network need to share information

• Client/server model– Client: uses some resource on another

computer– Server: provides that service

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Cabling LANs

• Peer-to-peer model– A computer acts as a peer with other

computers by acting as a client in some cases and a server in other cases

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Cabling LANs

• Peer-to-peer networking– Computers act as equals, providing services

to each other– To act as a server, a computer must decide to

share some or all of its resources with other peers

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Cabling LANs

PC Constellation Shares a Folder

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Cabling LANs

Another PC Shares Constellation’s Folder

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Cabling LANs

• Peer-to-peer networking– Have several advantages over client/server

networks• Simple to install• No special hardware required• Users control their own resources• No network administrator required

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Cabling LANs

• Peer-to-peer networking– Have several disadvantages compared to

client/server networks• Lack centralized security controls• Individuals must perform own backups• When user’s PC is acting as a server, performance

may suffer• Don’t work well with lots of users (limit of 10 or so)

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Cabling LANs

• Client/server networking– End users all act as clients– Dedicated computers, called servers, provide

all services– Use of multiple servers is common

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Cabling LANs

Client/Server Networking Model

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Cabling LANs

• Client/server networking– End user PCs are typically less expensive– Servers use a network operating system (NOS) that is

more expensive– Servers are more expensive and powerful– Centralized security is available– Centralized backups can be done

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Cabling LANs

Comparing Peer-to-Peer and Client Server Networking

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Cabling WANs

Simple Internetwork with Two Routers

Jagged line is a WAN link; often called a “lightning bolt”

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Cabling WANs

WAN Physical and Data Link Layers

• Routers can have both LAN and WAN interfaces– LAN interface requirements are more obvious

• RJ-45 jack needs a cable with an RJ-45 connector

– Some WAN interfaces are less obvious• Might be ISDN, DSL or cable

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Cabling WANs

WAN Physical and Data Link Layers• Router Serial Interfaces

– A serial interface connects to channel service unit/data service unit (CSU/DSU) with a serial cable

– The proper serial cable must be selected by the network engineer

– Router has WAN interface cards that have particular types of connectors

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Cabling WANs

Different Connectors on Router WAN Interface Cards

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Cabling WANs

WAN Link with Serial Cables, CSU/DSUs, and the Telco Shown

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Cabling WANs

Routers and WAN Cables• Many WAN links require a CSU/DSU• Connection to the CSU/DSU from router is with a

serial cable• Different CSU/DSU vendors use different cables• After selecting the CSU/DSU, order the correct

serial cable

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Cabling WANs

WAN Serial Cables Used with a Router

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Cabling WANs

Routers and WAN Cables• The CSU/DSU connects to a cable provided by

the Telco – usually an RJ-45 connector but with a different pinout

• Most companies standardize on connectors• Some routers have the CSU/DSU built in, so no

serial cable is needed• Network engineer must also consider what

protocol is being used

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Cabling WANs

OSI Layers 1 and 2 for Router Serial Links

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Cabling WANs

Cable, DSL and ISDN

• ISDN– Allows a WAN connection to be dialed like a

phone call– WAN link is not up and working all the time– Often used as a backup to a full-time, always-

on link

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Cabling WANs

Cable, DSL and ISDN• Several varieties of ISDN

– Basic Rate Interface uses already-installed phone lines

– Allows two concurrent 64 Kbps WAN links called “B channels”

– Has a signaling channel, the “D channel”

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Cabling WANs

Cable, DSL and ISDN• DSL and cable modems are now popular

– DSL uses phone lines– Cable modems use cable TV coaxial cable

• All three methods use a variation of Point-to-Point Protocol (PPP)

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Cabling WANs

ISDN, DSL and Cable: Cables and Connectors

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Cabling WANs

WAN Speeds• WAN links provided by Telcos can run at a large

variety of speeds– 2400 bps to multiples of 64 Kbps, up to 1.544 Mbps (a

T1 connection)– Traditional WAN speeds go above T1

• A T3 circuit runs at 28 times the speed of a T1• Synchronous Optical Network (SONET) can exceed 10 Gbps

• Faster links cost more money• Maximum length between devices is based in

part on speed

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Cabling WANs

Serial Cable Lengths in Comparison to Speed

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Cabling WANs

Choosing DCE and DTE Cables• Devices on both ends of a link must be synchronized• The telco provides clocking (synchronization)• The CSU/DSU monitors the clocking from the telco• Data communications equipment (DCE) - a device that

supplies clocking to another device• Data terminal equipment (DTE) – a device that receives

clocking from another device and adjusts its clock as needed

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Cabling WANs

DCE and DTE on a Typical WAN Link

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Cabling WANs

Choosing DCE and DTE Cables• In some cases, the router needs to operate as a

DCE device• This is common in lab situations like ours• We do this so we do not have to buy two

CSU/DSUs.

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Cabling WANs

Router as DCE: Back-to-Back Serial Communication

The connection between the two routers is a crossover serial connection.

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Cabling WANs

Fixed and Modular Routers• Cisco routers with permanently installed

interfaces are called “fixed-function” routers

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Cabling WANs

Fixed and Modular Routers• Cisco routers with the capability to add and

remove cards are called “modular” routers• Most current Cisco routers support at least some

modular interfaces• Each interface type has a unique number

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Cabling WANs

Cisco 1841 Modular Router

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Cabling WANs

Cisco 1841 Modular Router

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Cabling WANs

Router Console Cabling• Technically isn’t a LAN or WAN cable• To gain access to a Cisco switch or router for initial

configuration, you need to know about console ports and cables

• To configure or troubleshoot a Cisco router or switch– Connect a PC to the console port of the router or switch by using

a rollover cable– Configure a terminal emulator on the PC with the proper settings– Log into the router or switch by using the terminal emulator on

the PC

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Cabling WANs

Console Cabling

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Cabling WANs

Router Console Cabling• Many PCs have a nine-pin connector (DB-9)

which is used for serial communications• May be called a “serial port” or a “COM port”• Most routers and switches have an RJ-45 port for

a console port• Connect a PC to a router or switch using a

rollover cable and two RJ-45 connectors• Use an RJ-45 to DB-9 adapter on the PC end

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Cabling WANs

Router Console Cabling• Configure HyperTerminal or another terminal

emulator– 9600 bps– 8 data bits– No parity– 1 stop bit– No flow control

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Cabling WANs

Router Auxiliary Port• Routers also have an auxiliary port• Used for “out of band” (not through the network)

management• A modem may be connected to the auxiliary port• The network engineer may call the router and

make changes and troubleshoot problems over the phone line

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Summary

• Ethernet is the most widely used LAN technology

• Ethernet technologies provide a variety of speeds from 10 Mbps to 10 Gbps

• A NIC’s connector must match the media– Coax typically uses BNC connectors– STP and UTP use RJ-45 connectors– Fiber-Optic uses ST, SC or MT-RJ connectors

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Summary

• Twisted-pair cabling must use the correct pinout to work properly

• A crossover cable is used to connect two similar devices, such as switches

• A straight-through cable connects two different devices, such as a PC and a switch

• A rollover cable connects a PC to the console port of a router or a switch

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Summary

• Repeaters regenerate and retime network signals and let them travel a longer distance

• Hubs act as multiport repeaters and provide a central device to connect devices in a star physical topology

• Hubs are sometimes called concentrators• Bridges and switches use logic at Layer 2 of the

OSI model to decide when to forward frames or when not to forward (filter) them

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Summary

• Bridges and switches examine the destination MAC address of the frame and compare it to a list of MAC addresses and ports

• Because bridges and switches do not forward traffic unless necessary, they provide more bandwidth than hubs and repeaters and greatly improve network performance

• LAN switches provide the same basic functions as a bridge, but have a large number of ports that act as a concentration point

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Summary

• Today’s switches are so much faster than bridges that vendors such as Cisco no longer sell bridges

• Switches support a large variety of extra features, such as VLANs

• Wireless networks can be created with much less cabling than other networks

• Wireless AP’s connect to the rest of the network with an Ethernet cable

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Summary

• Wireless devices use transmitters and receivers to convert bits to EM waves (transmitter) and then back to bits at the destination (receiver)

• Two most common types of wireless technologies used for networking are IR and RF

• Typically computers use a peer-to-peer or client/server network model

• In both models, one computer acts as a client and another acts as a server

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Summary

• In peer-to-peer networks, networked computers act as equal partners

• In client/server networks, network services are located on a computer called a server and end-user computers always act as clients

• Routers are responsible for routing packets from source to destination computers

• Routers typically connect to a wide range of networking media, including different WAN (ISDN, DSL, CABLE) and LAN (Ethernet) types

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Summary

• Each WAN type requires some type of media and connector

• When a router’s serial interface is used, the cable type is determined by– Physical connector on the router– Physical interface on the CSU/DSU

• Router interface can be DCE or DTE, but is usually a DTE interface

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Summary

• A router serial WAN link can be DCE or DTE

• DCE provides clock synchronization; DTE adjusts its clock to match DTE end

• Traditionally, a router is a DTE device and a CSU/DSU is a DCE device (except in lab situations where no CSU/DSUs are used)

Networking Basics CCNA 1 Chapter 5

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